Electrocoating compositions are known and disclosed in Gilchrist patents such as U.S. Pat. Nos. 3,351,675; 3,362,899; 3,575,909; and 3,351,575; and the disclosures thereof are incorporated herein by reference.
Prior art electrocoating compositions ordinarily are based on acrylic polymers or copolymers wherein copolymers typically contain copolymerized polymer units of epoxy, polyester, phenolic, aminoplast resin, or phenolplast resins. These electrocoating compositions, however, lack one or more highly desirable physical integrity properties such as toughness, abrasion resistance, impact resistance, flexibility, chemical resistance, solvent resistance, mar resistance, or good weathering properties.
It now has been found that substantially improved electrocoating compositions can be produced from polyurethane-acrylic copolymers produced by first forming a peroxide terminated polyurethane copolymer, and then coreacting the peroxide-polyurethane copolymer with acrylic monomers to produce a polyurethaneacrylic copolymer. The copolymer can include minor amounts of carboxyl or amine containing monomer so as to render the polymer dispersable in water and provide a dilute electrocoating composition for coating either anode or cathode substrates. The cured electrocoated protective coating particularly exhibits improved toughness, impact resistance, flexibility, chemical resistance, solvent resistance, mar and scratch resistance, good weather resistance, good corrosion resistance, as well as other desirable film integrity properties. These and other advantages will become more apparent by referring to the Detailed Description of the Invention.